Optical flow cell for tribological systems

ABSTRACT

An optical flow is disclosed having a shell with a first portion and a second portion. The first portion provides a light entry aperture, and the second portion provides an imaging aperture. An inlet tube and an outlet tube are retained between the first portion and the second portion. A viewing assembly is retained between the first portion and the second portion. The viewing assembly includes a reference plate and a flow channel. The flow channel fluidly communicates with the inlet tube and the outlet tube. The reference plate extends from the shell to serve as a repeatable reference point for properly positioning the optical flow cell.

TECHNICAL FIELD

The present invention relates generally to fluid inspection systems.More particularly, the invention relates to an optical flow cell throughwhich the fluid under inspection passes. Specifically, the inventionrelates an optical flow cell which provides an accurate reference pointfor repeatable analysis of the fluid by an imaging system contained inthe fluid inspection system.

BACKGROUND ART

It is known to provide fluid sampling devices using optical near-fieldimaging. Such a device is employed to determine quantity, size, physicalcharacteristics, and types of particulate matter in fluids. Examples offluids which are monitored in such a system are lubricating oils used inengines and rotating machinery; hydraulic fluids used in equipment; andfluids used in industrial quality control, food processing, medicalanalysis, and environment control. In its most common use, such a devicemonitors engine oil for particulate debris, wherein a quantity, size,and shape of particulates correspond to an engine condition, and canalert one to particular problems with the engine. Predicting failure iscritically important in aircraft engines to avoid accidents and loss oflife.

The early stages of engine wear cause small particulate matter, of about50 microns or less in size, to be generated. These particulates havecharacteristic shapes indicative of the type of wear produced byspecific wear mechanisms. As the wear process progresses, the quantityand size of particulates increase. Accordingly, sensing and identifyingsmaller particles allows early identification of faults, thus, allowingmore time for corrective maintenance and preventing unexpectedcatastrophic failures.

Although current devices such as the optical flow cell disclosed in U.S.Pat. No. 6,104,483, which is incorporated herein by reference, aresufficient in their stated purpose, such devices can be difficult tomass produce because they are manufactured using a potting process. Forexample, during the potting process, a viewing assembly along with aninlet tube and an outlet tube are positioned in a mold, and the mold isthereafter filled with a bonding material (i.e. epoxy resin).

The bonding material ultimately cures around the inlet tube, outlettube, and viewing assembly to form the body of the optical flow cell.However, placement of the above-discussed components in the mold, andproviding access to the viewing assembly is difficult. For example, thepositioning of the inlet tube, outlet tube, and viewing assembly must beprecisely accomplished. Therefore, considerable time is spent arrangingthe components in the mold, and insuring that the components are alignedas the bonding material fills the mold. Furthermore, to insure accessthrough the body to the viewing assembly, various plungers or otherinserts must be used to form a light entry aperture and an imagingaperture. The plungers or other inserts are positioned on either side ofthe viewing assembly prior to filling the mold with bonding material.The placement of the plungers or other inserts further complicatesplacement of the components in the mold, and the overall manufacture ofthe optical flow cell.

After the bonding material cures, a “potted” part is removed from themold, and the plungers or other inserts, as well as extraneous epoxyresin are trimmed from the part. Thereafter, the part is cleaned, andadditional epoxy is applied around the periphery of the light entryaperture to form a finished optical flow cell.

As can be appreciated, manufacture of such an optical flow cell is atime-consuming process. Moreover, precise positioning of theabove-discussed components in the mold is difficult, thereby requiringadditional skilled labor for assembly.

Therefore, there is a need for an optical flow cell which is relativelysimple to manufacture. Such an optical flow cell should eliminate theneed to use a potting process during manufacture, and be composed ofpre-formed structural components. Such components should allow formanufacture of such an optical flow cell within small tolerances, andthereby provide for repeatable reference points.

DISCLOSURE OF THE INVENTION

In general, the present invention contemplates an optical flow cellhaving a shell with a first portion and a second portion, wherein thefirst portion provides a light entry aperture, and the second portionprovides an imaging aperture, an inlet tube and an outlet tube retainedbetween the first portion and the second portion, and a viewing assemblyretained between the first portion and the second portion, wherein theviewing assembly includes a reference plate and a flow channel, the flowchannel fluidly communicating with the inlet tube and the outlet tube,and the reference plate extending from the shell to serve as arepeatable reference point for properly positioning the optical flowcell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a flow cell a fluid inspection systemwhich employs an optical flow cell made in accordance with the conceptsof the present invention.

FIG. 1A is a top perspective view of the optical flow cell of FIG. 1;

FIG. 1B is a bottom perspective view of the optical flow cell of FIG. 1;

FIG. 1C is an exploded view of the optical flow cell showing a first anda second portion of a two-piece shell of the optical flow cell;

FIG. 2A is a top perspective view of the first portion;

FIG. 2B is a bottom perspective view of the first portion;

FIG. 3A is a top perspective view of the second portion;

FIG. 3B is a bottom perspective view of the second portion; and

FIG. 4 is a cross sectional view of a viewing assembly duringmanufacture thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, and more particularly to FIGS. 1, 1A and 1B,the optical flow cell of the present invention is designated generallyby the numeral 10. The optical flow cell 10 is provided within a fluidsample inspection system 12 as seen in FIG. 1 to aid the analysis of asample fluid material (not shown). A brief discussion of the fluidsample inspection system 12 will be provided, and then followed by adetailed discussion of the optical flow cell 10.

A pressure source 13 may be coupled to an input container 14 of thesample fluid material. Normally, the input container 14 contains oilsthat are used to lubricate machine parts, such as engines andtransmissions, or other fluid which contains particles that need to beevaluated.

Application of pressure generated by the pressure source 13 to the inputcontainer 14 causes the sample fluid material to flow to an input, andthrough the optical flow cell 10 for analysis. Coupled to an output ofthe optical flow cell 10 may be a pump 16, which is used to draw thesample fluid material through the optical flow cell 10. Those skilled inthe art will appreciate that the pressure source 13 and the pump 16 maybe employed in conjunction with one another, or may be operatedseparately to pass the sample fluid material through the optical flowcell 10. After passing through the optical flow cell 10, the samplefluid material is deposited into an output container 18 for storage, orother purposes.

In the fluid sample inspection system 12, a plate 22 supports theoptical flow cell 10. Also supported by the plate 22 is a light source24, which in the preferred embodiment, employs a laser diode withassociated collimating optics to direct light through a viewing assemblyof the optical flow cell 10 and into the sample fluid material. Thelight generated by the light source 24 impinges on the sample fluidmaterial, and generates an image (or shadow) which can be detected by animaging system 26 that is also supported by the plate 22. The imagingsystem 26 is coupled to a processor-based display system 27 forclassifying the particles, for determining the number of particlescontained within the sample, and for analyzing other features of thefluid.

An alternative light source 28, which may be used in conjunction with,or in alternative to the light source 24, may be positioned on anopposite side of the optical flow cell 16. The light source 28 mayproject a white light to facilitate the detection of the particle'scolor for further classification or analysis.

Referring now to FIGS. 1A, 1B, and 1C, it can be seen that the opticalflow cell 10 according to the present invention includes a two-pieceshell 30. The two-piece shell 30 includes a first portion 31 and asecond portion 32. When assembled, the first portion 31 and the secondportion 32 support an inlet tube 34, an outlet tube 35, and a viewingassembly 36.

To facilitate transmission of light into the fluid sample material, thefirst portion 31 provides a light entry aperture 38, and the secondportion provides an imaging aperture 39. When the optical flow cell ispositioned in the fluid sample inspection system 12, the light entryaperture 38 is positioned proximate the light source 24, and the imagingaperture 39 is positioned adjacent the imaging system 26. As such, thelight entry aperture 38 and imaging aperture 39 allow light transmissionthrough, and visual access to the viewing assembly 36 and the samplematerial moving through the optical flow cell 10.

The inlet tube 34, the outlet tube 35, and the viewing assembly 36 areultimately retained between the first portion 31 and the second portion32. The inlet tube 34 and the outlet tube 35 are respectively providedwith an inlet fitting 42 and an outlet fitting 43. The inlet fitting 42and the outlet fitting 43 are both threaded and allow the conduits (notshown) from the input container 14 and output container 18 to berespectively attached thereto.

As discussed above, the sample fluid material initially contained in thecontainer 14 is transferred by the operation of pressure source 13 andpump 16 through the optical flow cell 10. Aiding the passage (or flow)of the sample fluid material through the optical flow cell 10 is theconfiguration of the first portion 31 and second portion 32. Forexample, the first portion 31 and second portion 32 include sectionswhich are canted to impact the orientation of the inlet tube 34 andoutlet tube 35 when contained therein. Moreover, these sectionstransition the sample fluid material between the circularcross-sectioned inlet tube 34 and viewing assembly 36, and betweenviewing assembly 36 and the circular cross-sectional outlet tube 35.

As seen in FIGS. 2A and 3A, the first portion 31 and the second portion32 are configured to mate with and accept one another, as well as theinlet tube 34, the outlet tube 35, and the viewing assembly 36. Thefirst portion 31 and second portion 32 are manufactured of polymermaterials ideally through an injection molding process. Therefore, themanufacture of the first portion 31 and second portion 32 can berelatively inexpensive, and can accomplished to close tolerances.

The first portion 31 includes a base 50 extending between an inlet end51 and an outlet end 52. A first channel 54 is defined between segments55 and 56 which extend upwardly from the base 50. Also extendingupwardly from the base 50 are sloped segments 57 and 58, and rail sets59. The rail sets 59 partially define the boundaries of the slopedsegments 57 and 58, and as discussed below, aid in the engagement of thefirst portion 31 and second portion 32.

Like the first portion 31, the second portion 32 includes a base 60extending from an inlet end 61 to an outlet end 62. Furthermore, asecond channel 64 is defined between sloped segments 67 and 68 whichextend upwardly from the base 60. Partially defining the boundaries ofthe sloped segments 67 and 68 are ridge sets 69. Like the rail sets 59provided on the first portion 31, the ridge sets 69 aid in theengagement of the first portion 31 and second portion 32.

When the first portion 31 and the second portion 32 are interfaced withone another the close tolerances provide for a “snug” fit, where thesloped segments 57, 58 are positioned adjacent to and engage the slopedsegments 67, 68, respectively. Furthermore, the first channel 54cooperates with the second channel 64 to define a space for receivingand accommodating the viewing assembly 36. To that end, the surfaces 71Aand 71B extending across the sloped segments 57 and 58, respectively,form supplementary angles in relation to the surfaces 72A and 72Bextending across the sloped segments 67, 68, respectively. That is, theangle of the surface 71A is supplementary with respect to the angle ofthe surface 72A, and the angle of the surface 71B is supplementary withrespect to the angle of the surface 72B. As such, the orientation of thesloped surfaces 71A, 71B and sloped surfaces 72A, 72B allow the firstportion 31 and second portion to interface without significant gapsbetween these surfaces, although gaps may be permitted depending uponthe sizing of the rails sets 59 and ridge sets 69.

When the first portion 31 and second portion 32 are engaged, the railsets 59 provided along the sloped segments 57, 58, and the ridge sets 69provided along the sloped segments 67, 68 further enhance the interfaceof the first portion 31 and second portion 32. For example, when thetwo-piece housing 30 is assembled, the rail sets 59 are received in theridge sets 69, thereby properly locating the first portion 31 withrespect to the second portion 32.

As discussed above, the angles of the sloped segments 57, 58 and slopedsegments 67, 68 angularly orient the inlet tube 34 and outlet tube 35with respect to the first portion 31 and second portion 32. For example,as seen in FIGS. 2A and 3A, the first portion 31 and the second portion32 each have receiving notches for orienting the inlet tube 34 and theoutlet tube 35. The first portion 31 includes an inlet tube receivingnotch 74 and an outlet tube receiving notch 75 formed within the slopedsegments 57, 58, respectively. Furthermore, the second portion includesan inlet tube receiving notch 78 and an outlet tube receiving notch 79formed within the sloped segments 67 and 68, respectively.

Ultimately, when the housing two-piece shell 30 is assembled the inlettube receiving notch 74 opposes the inlet tube receiving notch 78, andthe outlet tube receiving notch 75 opposes the outlet tube receivingnotch 79. Therefore, when the inlet tube 34 and outlet tube 35 areretained between the first portion 31 and second portion 32, the inlettube 34 is positioned between the inlet tube receiving notches 74 and78, and the outlet tube 35 is captured between the outlet tube receivingnotches 75 and 79.

Provided adjacent the inlet tube receiving notch 74 and the outlet tubereceiving notch 75, and formed within the sloped segment 57, 58 aresemi-cylindrical transition notches 82 and 83. The semi-cylindricaltransition notches 84 and 85 are oppositely oriented on either side ofthe first channel 54. Furthermore, provided adjacent the inlet tubereceiving notch 78 and the outlet tube receiving notch 79, and formedwithin the sloped segments 67, 68 are first specially-configuredtransition notches 84 and 85 that are oppositely oriented on either sideof the second channel 64. The first specially-configured transitionnotches 78 and 79 include first end portions 86, tapered portions 87,and second end portions 88. Because the first specially-configuredtransition notches 78 and 79 are oppositely oriented on either side ofthe second channel 64, the tapered portions 87 thereof cantedoppositely.

When the two-piece housing 30 is assembled, the semi-cylindrical notches82 and 83 oppose the first specially-configured transition notches 84and 85. Like the semi-cylindrical transition notches 82 and 83, thefirst end portions 86 have radii matching the radii of the inlet tube 34and outlet tube 35.

Provided adjacent the semi-cylindrical transition notches 82 and 83, andformed within the segments 55, 56 are second specially-configuredtransition notches 90 and 91. When the two-piece housing 30 isassembled, the second specially-configured transition notches 90 and 91are opposed to a portion of the viewing assembly 36 (a reference plate98) because of the comparatively large width of the first channel 54 ascompared to the second channel 64. Like the first specially-configuredtransition notches 84 and 85, the second specially-configured transitionnotches 90, 91 also have a first end portion 92, a tapered portion 93,and a second end portion 94.

The construction of the viewing assembly 36 is best seen in FIG. 4, andincludes the reference plate 98 and a sealing plate 99. The plates 98and 99 are typically glass plates with excellent optical properties. Thereference plate 98 is the longer of the two plates, and extends beyondthe edges of the two-piece housing 30 (as seen in FIGS. 1A and 1B).Furthermore, the reference plate 98 has a closely controlled thickness,which provides a mechanical datum for a repeatable focus position forthe imaging system 26.

As seen in FIG. 4, the reference plate 98 is adapted to accept twospaced apart substantially parallel bonding strips 100. In addition toadhering the reference plate 98 and the sealing plate 99 together, thebonding strips serve to separate the plates from one another to define aflow channel 102 therebetween.

The flow channel 102 has a rectangular cross section, and theabove-described configuration of the first portion 31 and second portion32 between the inlet tube 34 and the viewing assembly 36 and between theoutlet tube 35 and the viewing assembly 36 provides a smooth and uniformtransition between the circular cross-section inlet tube 34 and outlettube 35, and the rectangular cross-sectioned flow channel 102.

Before the inlet tube 34, the outlet tube 35, and the viewing assembly36 are inserted between the first portion 31 and a second portion 32,the interior surfaces of the first and second portions 31 and 32 areexposed to a corona treatment. The material utilized in manufacturingthe first portion 31 and a second portion 32 was selected to be highlyresistant to the chemical environment it will operate in, and the coronatreatment serves to increase the surface energy thereof prior tobonding.

To further enhance the bonding of the first portion 31 and the secondportion 32 together, both portions are provided with various apertures104. Therefore, during the bonding process, a bonding material (i.e.epoxy resin) is injected into the various apertures 104 to ultimatelyflow between the first and second portions 31 and 32 to join thetwo-piece shell 30 together.

In addition, bonding channels 106, 107 are provided on the interiorsurfaces of the first portion 31 and a second portion 32, respectively.For example, on the first portion 31, the bonding channels 106 are cutinto the segments 55, 56, sloped segments 57, 58, and first channel 54,and on the second portion 32, the bonding channels 107 are cut into thesecond channel 64. The channels 106, 107 direct the flow of epoxy resinbetween the first portion 31 and second portion 32 during injection, andtherefore, provide good adhesion between all of the required surfaces.Additionally, the inlet tube 34 and the outlet tube 35 include ribs 110which enhance the rotational mechanical stability of the inlet tube 34and the outlet tube 35 in the two piece shell 30, and enhance the leakprevention in the optical flow cell 10.

When the optical flow cell 10 is assembled, the transition providedbetween the inlet tube 34 and the flow channel 102, and between theoutlet tube 35 and the flow channel 102 allows the sample fluid materialto efficiently transition between the circular cross-sectioned inlettube 34 and the rectangular cross-sectioned flow channel 102 and betweenthe rectangular cross-section flow channel 102 and the circularcross-sectioned outlet tube 35.

For example, the sample fluid material exiting the inlet tube 34 entersthe area defined by the semi-cylindrical transition notch 82 and thefirst specially-configured transition notch 84. The tapered portion 87(between the first end portion 86 and the second end portion 88) servesto flatten the flow pattern of the fluid sample material. Thereafter,the sample fluid material enters the area defined by the secondspecially-configured transition notch 90 and the reference plate 98. Thetapered portion 93 (between the first end portion 92 and the second endportion 94) also serves to flatten the flow pattern of the fluid samplematerial. The flattening of the flow pattern of the sample fluidmaterial effectively transitions the flow from the inlet tube 34 to theflow channel 102. As such, the configuration of the first portion 31 andsecond portion 32 prepares the sample fluid material to smoothly flowfrom the circular cross-sectioned inlet tube 34 to the rectangularcross-sectioned flow channel 102.

During travel through the flow channel 102, the fluid sample materialcan be analyzed by the fluid sample inspection system 12. After beinganalyzed by the fluid sample inspection system 12, the sample fluidmaterial exits the flow channel 102. Upon exiting the flow channel 102,the sample fluid material enters the area defined by the secondspecially-configured transition notch 91 and the reference plate 98. Thetapered portion 93 of the second specially-configured transition notch91 and the tapered portion 93 of the second specially-configuredtransition notch 90 are canted oppositely. As such, rather than servingto flatten the flow of the sample fluid material, the tapered portion 93of the second specially-configured transition 91 allows flow of thesample fluid material to expand.

Thereafter, the flow of the sample fluid material enters the areadefined by the semi-cylindrical transition notch 83 and firstspecially-configured transition notch 85. Again, like tapered portions93, the tapered portions 97 of the first specially-configured transitionnotch 85 and of the first specially-configured transition notch 84 arecanted oppositely. As such, rather than serving to flatten flow of thesample fluid material, the tapered portion of the firstspecially-configured transition notch 85 allows the flow of the samplefluid material to expand. The transitioning provided by the firstportion 31 and second portion 32 downstream of the flow channel 102allows the flow pattern of the sample fluid material (flattened by itstransition into and through the flow channel 102) to be modified beforeentering the outlet tube 35. As such, the configuration of the firstportion 31 and second portion 32 prepares the sample fluid material tosmoothly flow from the rectangular cross-sectioned flow channel 102 tothe circular cross-sectioned outlet tube 35.

Consequently, the optical flow cell 10 has many advantages over theprior art. By employing a reference plate 98 that extends beyond theedges of the two-piece housing 30, the reference plate 98 is easily usedas a repeatable reference point to place the optical flow cell 10 in apredetermined location in the imaging system 26. As those skilled in theart will appreciate, proper positioning of the optical flow cell 10 (andthe viewing assembly 36) in the imaging system 26 is of criticalimportance because of the typical small size of the particulate matterbeing monitored. Moreover, because the optical flow cell 10 ismanufactured within small tolerances, the reference point provided bythe reference plate 98 is repeatable between alternative examples of theoptical flow cell 10 installed in the imaging system 26. Furthermore,the configuration of the first portion 31 and second portion 32 providea smooth flow pattern for the sample fluid material through the opticalflow cell. Such transitioning of the sample fluid material decreasesturbulence, and allows the particles suspended in the sample fluidmaterial to be analyzed by the fluid sample inspection system 12.Moreover, the use of first portion 31 and second portion 32 arerelatively inexpensive to manufacture, and because of theirconfigurations, provide for faster assembly of the optical flow cell 10.In fact, the first portion 31 and second portion 32 serve to eliminatethe time-consuming potting process associated with the prior art, andsimultaneously increase the tolerances under which the optical flow cell10 is manufactured. As such, the close tolerances associated with theoptical flow cell 10 provide for repeatable reference points. That is,the close tolerances insure substantially similar dimensions betweenmanufactured optical flow cells 10, thereby substantially eliminatingtime consuming adjustments to the fluid sample inspection system 12 toaccommodate dimensional differences associated with prior art opticalflow cells.

Thus, it should be evident that the optical flow cell 10 disclosedherein carries out one or more of the objects of the present inventionset forth above and otherwise constitutes an advantageous contributionto the art. As will be apparent to persons skilled in the art,modifications can be made to the preferred embodiment disclosed hereinwithout departing from the spirit of the invention, the scope of theinvention herein being limited solely by the scope of the attachedclaims.

1. An optical flow cell, comprising: a shell having a first portion anda second portion, wherein said first portion provides a light entryaperture, and said second portion provides an imaging aperture; an inlettube and an outlet tube retained between said first portion and saidsecond portion; and a viewing assembly retained between said firstportion and said second portion, wherein said viewing assembly includesa reference plate and a flow channel, said flow channel fluidlycommunicating with said inlet tube and said outlet tube.
 2. An opticalflow cell according to claim 1, wherein said reference plate extendsfrom said shell, and serves as a repeatable reference point to properlyposition the optical flow cell.
 3. An optical flow cell according toclaim 1, wherein said reference plate is separated from a sealing plateby bonding strips, said flow channel being formed between said bondingstrips,
 4. An optical flow cell according to claim 1, wherein said firstportion and said second portion each include channels adapted toaccommodate said viewing assembly, when said viewing assembly isretained between said first portion and said second portion.
 5. Anoptical flow cell according to claim 1, wherein said first portionincludes an inlet tube receiving notch and an outlet tube receivingnotch and said second portion includes an inlet tube receiving notch andan outlet tube receiving notch, and when said inlet tube and said outlettube are retained within said shell, said inlet tube is positionedbetween said inlet tube receiving notches and said outlet tube ispositioned between said outlet tube receiving notches.
 6. An opticalflow cell according to claim 1, wherein said inlet tube has a circularcross section, said outlet tube as a circular cross section, and saidflow channel has a rectangular cross section, said first portion andsaid second portion configured to smoothly transition flow of a samplefluid material between said first outlet tube and said flow channel andbetween said flow channel and said second outlet tube.
 7. An opticalflow cell according to claim 6, further comprising a first channelprovided on said first portion, and semi-cylindrical transition notchesoppositely oriented on either side of said channel, a second channelprovided on said second portion, and first specially-configuredtransition notches are oppositely oriented on either side of said secondchannel, said specially-configured transition notches each including atapered portion, and said semi-cylindrical transition notches and saidfirst specially-configured transition notches opposed to one another oneither side of said channel when said optical flow cell is assembled. 8.An optical flow cell according to claim 7, wherein secondspecially-configured transitions notches are provided adjacent saidsecond semi-cylindrical transition notches on said first portion, saidsecond specially-configured transition notches opposing a plate of saidviewing assembly when said optical flow cell is assembled.
 9. An opticalflow cell, comprising: a shell having a first portion and a secondportion, wherein said first portion provides a light entry aperture, andsaid second portion provides an imaging aperture; an inlet tube and anoutlet tube retained between said first portion and said second portion;and a viewing assembly retained between said first portion and saidsecond portion, said viewing assembly including a reference plate and aflow channel, said flow channel fluidly communicating with said inlettube and said outlet tube, wherein said inlet tube has a circular crosssection, said outlet tube as a circular cross section, and said flowchannel has a rectangular cross section, said first portion and saidsecond portion configured to smoothly transition flow of a sample fluidmaterial between said first outlet tube and said flow channel andbetween said flow channel and said second outlet tube.